Large amounts of industrial and motor oil are used every day around the world in various industries and/or engines. The resulting product after the oil is hard to dispose of and in most cases an environmental hazard. On the other hand, used oil, once properly treated could be a potential resource for reuse in a variety of different industries.
Many different approaches exist for refining various types of used oil. However, most of these methods are either inefficient and/or result in low quality refined oil or are too complex and expensive to use. For example, one of the most commonly used methods of refining used oil which uses sulfuric acid and ash produces a lube stock suited for use as a low-grade motor oil or as a grease base. Moreover, this process results in producing a byproduct of acid sludge and clay which is environmentally hazardous and difficult to dispose of.
Other existing methods include vacuum distillation with thin film evaporation, evaporation of thin film with hydrotreating of distilled oil to lube stock, thermal dehumidification with hydrotreatment of the oil, and solvent extraction with hydrotreatment. Each of these methods exhibits some disadvantages. For example, the distillation and thermal dehumidification techniques are complex in nature due, at least in part, to high temperatures required for the processes. Moreover, in general, these processes use a lot of energy, which can be costly. The solvent extraction process also requires a large amount of solvent, which is usually several (at least four to six) times the volume of the oil being treated, and such leads to high costs and solvent recovery problems.
Therefore, a need exists for providing an improved system and method of refining used oil that results in high quality refined oil, while producing small quantities of undesirable waste products, and the system is inexpensive to design and operate.